1. Field of the Invention
The present invention concerns a bearing structure for a rotor blade of a wind turbine. In particular, the invention relates to a composite structure rotor blade. The invention further concerns a process for the production of a shaped body, in particular a rotor blade, of a fiber composite structure, comprising the following steps: producing shells forming the outer contour of the shaped body, producing bearing structures of fiber strands of predetermined length which are impregnated with a hardening composite material, and transporting the bearing structure into the shells.
2. Description of the Related Art
A process has long been known in the field of wind power to produce rotor blades with a dependable joining between the bearing structure and the shells forming the outer contour of the rotor blade as the same materials are used in each case.
In that respect, half-shell portions, for example of fiber composite material such as glass fiber and epoxy resin are produced, and these determine the external shape of the rotor blade. As such rotor blades often reach lengths of more than 50 meters, loads occur, which must be absorbed and dissipated. That is effected by way of the bearing structure provided in the rotor blade.
A known bearing structure comprises what are called roving webs. These involve strands of fiber material such as carbon fiber or, preferably because of the low cost, glass fiber. Those strands extend in part continuously over the entire length of the bearing structure or the rotor blade. The number of webs also increases with increasing proximity to the rotor blade root in order to absorb and dissipate the higher loads by virtue of a greater blade thickness and blade depth.
In order to achieve an adequate load-bearing capability, a suitably large number of those roving webs is used. They are impregnated with a polymer such as for example epoxy resin before being fitted into the prefabricated rotor blade shell. It will be appreciated that the impregnation operation can be effected equally by feeding the polymer from the outside and also by an injection process. The impregnated roving webs are then fitted into the shell of the rotor blade at the intended positions. As the rotor blade is made from the same material, there is an excellent join between the shell and the roving webs.
As those roving webs are laid ‘wet’ in the shell however deformations can easily occur in that procedure as those wet webs are not flexurally stiff. Such deformations are also referred to as ‘undulations’ and after hardening result in a spring effect at that location. That adversely affects the stiffness of the bearing structure or the rotor blade.
In addition, hardening of the polymer is an exothermic process in which heat is correspondingly given off to the exterior. In the case of bearing structures comprising a large number of roving webs, a correspondingly large amount of epoxy resin is also required in order to produce an adequate join. The exothermic reaction is correspondingly intensive and the amount of heat given off is correspondingly high.
As general state of the art attention is to be directed to DE 44 23 115 A1 and DE-AS No 1 264 266.